The code was checking for a non-existent macro `HDIO_GETGIO` instead of
`HDIO_GETGEO`, which caused the ioctl() call to never be executed.
This resulted in start_sector always being set to 0, even when the
partition actually starts at a different sector (e.g., 2048).
This bug affects:
- lib/libf2fs.c: get_device_info() function (lines 967, 1076)
- tools/fibmap.c: stat_bdev() function (lines 91, 108)
Reproducer:
1. Create a partition starting at sector 2048:
# parted -s /dev/sdb mklabel gpt
# parted -s /dev/sdb mkpart primary 2048s 32GiB
2. Verify the partition start sector:
# cat /sys/block/sdb/sdb1/start
2048
3. Format with f2fs-tools (before fix) and verify incorrect calculation:
# mkfs.f2fs /dev/sdb1
# Info: zone aligned segment0 blkaddr: 512
The calculation happens in
mkfs/f2fs_format.c:f2fs_prepare_super_block():
With default values:
- blk_size_bytes = 4096
- c.blks_per_seg = 512
- c.segs_per_sec = 1
- c.secs_per_zone = 1
- zone_size_bytes = blk_size_bytes * c.secs_per_zone
* c.segs_per_sec * c.blks_per_seg
= 4096 * 1 * 1 * 512 = 2,097,152 bytes (2MB)
- alignment_bytes = zone_size_bytes (for non-zoned or single device)
With c.start_sector = 0 (bug case):
- zone_align_start_offset
= ((c.start_sector * DEFAULT_SECTOR_SIZE +
2 * F2FS_BLKSIZE + alignment_bytes - 1) /
alignment_bytes * alignment_bytes) -
(c.start_sector * DEFAULT_SECTOR_SIZE)
= ((0 * 512 + 2 * 4096 + 2,097,152 - 1) /
2,097,152 * 2,097,152) - (0 * 512)
= ((8,192 + 2,097,152 - 1) / 2,097,152 * 2,097,152) - 0
= 2,097,152 - 0 = 2,097,152 bytes (2MB)
- segment0_blkaddr = zone_align_start_offset / blk_size_bytes
= 2,097,152 / 4,096 = 512 blocks
This matches the output "segment0 blkaddr: 512".
With c.start_sector = 2048 (correct case):
- zone_align_start_offset
= ((2048 * 512 + 2 * 4096 + 2,097,152 - 1) /
2,097,152 * 2,097,152) - (2048 * 512)
= ((1,048,576 + 8,192 + 2,097,152 - 1) /
2,097,152 * 2,097,152) - 1,048,576
= 2,097,152 - 1,048,576 = 1,048,576 bytes (1MB)
- segment0_blkaddr = zone_align_start_offset / blk_size_bytes
= 1,048,576 / 4,096 = 256 blocks
4. Confirm the bug with gdb:
So the correct output should be "segment0 blkaddr: 256", not 512.
# gdb --args mkfs.f2fs /dev/sdb1
(gdb) b lib/libf2fs.c:1075
(gdb) run
1075 if (i == 0) {
(gdb) l
1075 if (i == 0) {
1076 #ifdef HDIO_GETGIO
1077 if (ioctl(fd, HDIO_GETGEO, &geom) < 0)
1078 c.start_sector = 0;
1079 else
1080 c.start_sector = geom.start;
1081 #else
1082 c.start_sector = 0;
1083 #endif
1084 }
(gdb) n
1082 c.start_sector = 0;
# At line 1076: #ifdef HDIO_GETGIO (bug - this macro doesn't exist)
# The ioctl() call at line 1077 is skipped, and execution goes
# directly to line 1082, setting c.start_sector = 0
After fix:
mkfs.f2fs output:
Info: zone aligned segment0 blkaddr: 256
gdb output:
(gdb) p c.start_sector
$1 = 2048
The ioctl() correctly retrieves the partition start sector (2048),
and zone_align_start_offset is calculated correctly, resulting in
segment0_blkaddr = 256.
Fixes: 43bb7b6c99fa ("f2fs-tools: build binaries in Mac")
Signed-off-by: Xiaole He <[email protected]>
